Many portable electronic devices utilize a portable, self contained, power source such as a battery to provide the necessary operating current and voltage when the device is not connected to a more permanent power source such as an electrical outlet. Frequently the battery is a rechargeable type that may be characterized, for example, as a nickel cadmium, lithium ion or lead acid type. Many different methods have been utilized to recharge such batteries while the battery resides within the parent portable device. In generic environments, a pair of copper wires is used to charge the battery. The leads of the charging wire are usually covered with an insulating layer and therefore unexposed. The leads make contact with the battery within the device when the leads are secured to a suitable terminal strip or socket mounted on the device.
In other environments a dock or socket based charging system, utilizing exposed electrical contacts, is employed. When a docking station is used, the device can be charged relatively quickly by placing the device directly on the contacts of the charging portion of the docking station. In a clinical environment exposed charging contacts are usually desirable because the contacts can then be easily accessed for cleaning. However, the potential danger of exposed contacts in a clinical environment is substantial and thus there are many safety requirements that must be satisfied regarding patient isolation as well as the magnitude of any exposed voltages. In response to these regulatory and safety concerns, charging systems sometimes utilize a second set of contacts to detect that a device is properly docked before supplying the battery charging voltage. However, two sets of contacts are inherently undesirable because it increases the expense and opportunity for failure and there may not be enough room for them. In addition, some method is desired to confirm that a portable instrument is properly docked within the station and to permit the efficient transfer of electrical power to the portable instrument without regard to the supply voltage polarity. An electronic device identification system constructed according to the principles of the present invention addresses these deficiencies and related problems.